Silicon carbide (SiC) is expected to serve as a material for a next-generation semiconductor device. SiC has more excellent physical properties in comparison with silicon (Si): band gap, three times; breakdown field strength, approximately ten times; and thermal conductivity, approximately three times. A low loss semiconductor device which can operate at a high temperature can be realized by using such properties.
However, when a metal oxide semiconductor field effect transistor (MOSFET) is formed by using SiC, for example, there is a problem that carrier mobility is lowered. It is considered that a decrease in carrier mobility is due to a high density of an interface state existing between a silicon carbide layer and a silicon oxide layer functioning as a gate insulating layer.